1. Field of the Invention
The present invention relates to a multilayer fluid conduit for use in motor vehicles, with a first layer and a second layer surrounding the first layer, wherein the first and second layers are composed essentially of thermoplastic material and are integrally connected, and wherein electrically conductive particles are mixed into the thermoplastic material of the first layer.
2. Description of the Related Art
A multilayer fluid conduit of this type is disclosed in DE 198 31 898 A1. The fluid conduit is primarily used for liquid fuels, such as gasoline or diesel oil, however, the fluid line is also suitable for other hydrocarbon-containing fluids, particularly alcohol-containing fluids, for example, for brake liquids or glycol-containing cooling water. If such fluids contain water and/or alcohol, the thermoplastic material may hydrolytically decompose and become brittle if it comes for a longer period of time in contact with these fluids and at higher temperatures.
Therefore, it is the primary object of the present invention to provide a multilayer fluid conduit of the above-described type in which the long-term elasticity and long-term flexibility is maintained even at higher temperatures of up to at least 90xc2x0 C. when coming into contact with a hydrocarbon-containing fluid, such as liquid fuel and fuel vapors.
In accordance with the present invention, this object is met in a multilayer conduit in which the plastic material of the first layer is a functionalized cross-linked polyolefine or a functionalized cross-linked elastomer.
These plastic materials have the advantage that they do not become brittle even after long-term storage in fuels at temperatures of up to 90xc2x0 C. Cross-linking increases the thermal strength, at least for the short term, up to 150xc2x0 C., and the resistance to chemicals.
When the materials are functionalized, additional monomers are connected by grafting to existing macromolecules (polymers). This produces a new polymer, i.e., either a copolymer or a terpolymer, and the new polymer then has new functional end groups. During further processing at higher temperatures, these end groups are then capable of connecting in the melt to other end groups of chemically different polymers, such as polyamide or thermoplastic polyester. As a result, it is possible that an integral connection and adherence is achieved between two different molten materials.
Preferably, it is ensured that the functionalized cross-linked polyolefin is at least one of a first group which includes a polyolefin homopolymer, a polyolefin copolymer, a polyolefin terpolymer, an anhydride-grafted polyolefin, a glycidil methacrylate-grafted polyolefin, a maleic acid-grafted polyolefin and an elastomer-modified polyolefin.
Further, it can be ensured that the functionalized cross-linked thermoplastic elastomer is essentially a material of a group which includes polyamide, polyesters, glycidil methacrylate-grafted elastomers, maleic acid-grafted elastomers and functionalized rubbers, particularly acrylonitrile butadiene rubber (NBR), hydrated acrylonitrile-butadiene-rubber (HNBR) and ethylene-propyleneterpolymers (EPDM).
In addition, it is advantageous if the plastic material of the second layer is at least one of a second group which includes a polyolefin, a polyamide, a thermoplastic polyester, a polyacetal, a polyether ketone, a fluorothermoplastic material, a polyester elastomer and a thermoplastic elastomer.
Another possibility is that the plastic material of the first layer is mixed with at least one plastic material of the second layer.
Moreover, it is advantageous if the second layer is integrally connected to a third layer which surrounds the second layer, wherein the third layer is essentially of a thermoplastic material of which at least one of the first or second layers are made.
The third layer can also be integrally connected to a fourth layer which surrounds the third layer, wherein the fourth layer is essentially of a thermoplastic material composed of at least one plastic material of the first or second layers.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.